The EMC acts as a chaperone for membrane proteins.

Structure formation of membrane proteins is error-prone and thus requires chaperones that oversee this essential process in cell biology. The ER membrane protein complex (EMC) is well-defined as a transmembrane domain (TMD) insertase. In this study, we characterize an additional chaperone function of the EMC.

A helminth enzyme subverts macrophage-mediated immunity by epigenetic targeting of prostaglandin synthesis.

The molecular mechanisms by which worm parasites evade host immunity are incompletely understood. In a mouse model of intestinal helminth infection using (), we show that helminthic glutamate dehydrogenase (heGDH) drives parasite chronicity by suppressing macrophage-mediated host defense. Combining RNA-seq, ChIP-seq, and targeted lipidomics, we identify prostaglandin E (PGE) as a major immune regulatory mechanism of heGDH.

Development of an enabling platform biotechnology for the production of proteins.

Protein-based drugs are a mainstay of modern medicine. In contrast to antibodies, most of these need highly individualized production processes which often limits their development. Here, we develop an immunoglobulin domain tag (i-Tag), which can be fused to any protein of interest.

The DNA-binding induced (de)AMPylation activity of a Coxiella burnetii Fic enzyme targets Histone H3.

The intracellular bacterial pathogen Coxiella burnetii evades the host response by secreting effector proteins that aid in establishing a replication-friendly niche. Bacterial filamentation induced by cyclic AMP (Fic) enzymes can act as effectors by covalently modifying target proteins with the posttranslational AMPylation by transferring adenosine monophosphate (AMP) from adenosine triphosphate (ATP) to a hydroxyl-containing side chain. Here we identify the gene product of C.

Assembly-dependent Structure Formation Shapes Human Interleukin-23 versus Interleukin-12 Secretion.

Interleukin 12 (IL-12) family cytokines connect the innate and adaptive branches of the immune system and regulate immune responses. A unique characteristic of this family is that each member is anα:βheterodimer. For human αsubunits it has been shown that they depend on theirβsubunit for structure formation and secretion from cells.

Modeling of the human interleukin 12:receptor complex allows to engineer attenuated cytokine variants.

Interleukin 12 (IL-12) plays major roles in immune defense against intracellular pathogens. By activating T cells and increasing antigen presentation, it is also a very potent anti-tumor molecule. Strong immune activation and systemic toxicity, however, so far limit its potential therapeutic use.

A chemical probe unravels the reactive proteome of health-associated catechols.

Catechol-containing natural products are common constituents of foods, drinks, and drugs. Natural products carrying this motif are often associated with beneficial biological effects such as anticancer activity and neuroprotection. However, the molecular mode of action behind these properties is poorly understood.

Mechanistic insights into the aggregation pathway of the patient-derived immunoglobulin light chain variable domain protein FOR005.

Systemic antibody light chain (AL) amyloidosis is characterized by deposition of amyloid fibrils. Prior to fibril formation, soluble oligomeric AL protein has a direct cytotoxic effect on cardiomyocytes. We focus on the patient derived λ-III AL variable domain FOR005 which is mutated at five positions with respect to the closest germline protein.

The human signal peptidase complex acts as a quality control enzyme for membrane proteins.

Cells need to detect and degrade faulty membrane proteins to maintain homeostasis. In this study, we identify a previously unknown function of the human signal peptidase complex (SPC)-the enzyme that removes endoplasmic reticulum (ER) signal peptides-as a membrane protein quality control factor. We show that the SPC cleaves membrane proteins that fail to correctly fold or assemble into their native complexes at otherwise hidden cleavage sites, which our study reveals to be abundant in the human membrane proteome.

A comprehensive set of ER protein disulfide isomerase family members supports the biogenesis of proinflammatory interleukin 12 family cytokines.

Cytokines of the interleukin 12 (IL-12) family are assembled combinatorially from shared α and β subunits. A common theme is that human IL-12 family α subunits remain incompletely structured in isolation until they pair with a designate β subunit. Accordingly, chaperones need to support and control specific assembly processes.

Intramembrane client recognition potentiates the chaperone functions of calnexin.

One-third of the human proteome is comprised of membrane proteins, which are particularly vulnerable to misfolding and often require folding assistance by molecular chaperones. Calnexin (CNX), which engages client proteins via its sugar-binding lectin domain, is one of the most abundant ER chaperones, and plays an important role in membrane protein biogenesis. Based on mass spectrometric analyses, we here show that calnexin interacts with a large number of nonglycosylated membrane proteins, indicative of additional nonlectin binding modes.

Biogenesis and engineering of interleukin 12 family cytokines.

Interleukin 12 (IL-12) family cytokines are secreted proteins that regulate immune responses. Each family member is a heterodimer and nature uses shared building blocks to assemble the functionally distinct IL-12 cytokines. In recent years we have gained insights into the molecular principles and cellular regulation of IL-12 family biogenesis.

IL-30 (IL-27A): a familiar stranger in immunity, inflammation, and cancer.

Over the years, interleukin (IL)-27 has received much attention because of its highly divergent, sometimes even opposing, functions in immunity. IL-30, the p28 subunit that forms IL-27 together with Ebi3 and is also known as IL-27p28 or IL-27A, has been considered a surrogate to represent IL-27. However, it was later discovered that IL-30 can form complexes with other protein subunits, potentially leading to overlapping or discrete functions.

Quality control of mislocalized and orphan proteins.

A healthy and functional proteome is essential to cell physiology. However, this is constantly being challenged as most steps of protein metabolism are error-prone and changes in the physico-chemical environment can affect protein structure and function, thereby disrupting proteome homeostasis. Among a variety of potential mistakes, proteins can be targeted to incorrect compartments or subunits of protein complexes may fail to assemble properly with their partners, resulting in the formation of mislocalized and orphan proteins, respectively.

Specificity of AMPylation of the human chaperone BiP is mediated by TPR motifs of FICD.

To adapt to fluctuating protein folding loads in the endoplasmic reticulum (ER), the Hsp70 chaperone BiP is reversibly modified with adenosine monophosphate (AMP) by the ER-resident Fic-enzyme FICD/HYPE. The structural basis for BiP binding and AMPylation by FICD has remained elusive due to the transient nature of the enzyme-substrate-complex. Here, we use thiol-reactive derivatives of the cosubstrate adenosine triphosphate (ATP) to covalently stabilize the transient FICD:BiP complex and determine its crystal structure.

Fluorescent palladium(II) and platinum(II) NHC/1,2,3-triazole complexes: antiproliferative activity and selectivity against cancer cells.

Fluorescent Pd(ii) and Pt(ii) complexes bearing 4-methylene-7-methoxycoumarin (MMC) and 2,6-diispropylphenyl (Dipp) substituted NHC/1,2,3-triazole hybrid ligands are described. Depending on the reaction conditions two different ligand coordination modes are observed, i.e.

Influence of glycosylation on IL-12 family cytokine biogenesis and function.

The interleukin 12 (IL-12) family of cytokines regulates T cell functions and is key for the orchestration of immune responses. Each heterodimeric IL-12 family member is a glycoprotein. However, the impact of glycosylation on biogenesis and function of the different family members has remained incompletely defined.

Glycosaminoglycans bind human IL-27 and regulate its activity.

IL-27 is a cytokine of the IL-12 family, composed of EBI3 and IL-27p28. IL-27 regulates immune responses and also other physiological processes including hematopoiesis, angiogenesis, and bone formation. Its receptor, composed of IL-27Rα and gp130, activates the STAT pathway.

An anti-inflammatory eicosanoid switch mediates the suppression of type-2 inflammation by helminth larval products.

Eicosanoids are key mediators of type-2 inflammation, e.g., in allergy and asthma.

In case of stress, hold tight: phosphorylation switches PDI from an oxidoreductase to a holdase, tuning ER proteostasis.

Eukaryotic cells have evolved multiple responses that allow endoplasmic reticulum (ER) homeostasis to be maintained even in the face of acute or chronic stresses. In this issue, Yu et al (2020) describe how site-specific phosphorylation switches protein disulfide isomerase (PDI) from a folding enzyme to a holdase chaperone which regulates ER stress responses, thus highlighting PDI as a key player in ER homeostasis.

Site-Specific Protein Labeling with Fluorophores as a Tool To Monitor Protein Turnover.

Proteins that terminally fail to acquire their native structure are detected and degraded by cellular quality control systems. Insights into cellular protein quality control are key to a better understanding of how cells establish and maintain the integrity of their proteome and of how failures in these processes cause human disease. Here we have used genetic code expansion and fast bio-orthogonal reactions to monitor protein turnover in mammalian cells through a fluorescence-based assay.

Structural Insight into IAPP-Derived Amyloid Inhibitors and Their Mechanism of Action.

Designed peptides derived from the islet amyloid polypeptide (IAPP) cross-amyloid interaction surface with Aβ (termed interaction surface mimics or ISMs) have been shown to be highly potent inhibitors of Aβ amyloid self-assembly. However, the molecular mechanism of their function is not well understood. Using solution-state and solid-state NMR spectroscopy in combination with ensemble-averaged dynamics simulations and other biophysical methods including TEM, fluorescence spectroscopy and microscopy, and DLS, we characterize ISM structural preferences and interactions.